AbstractObjective: To compare the effect of self‐etching primers and phosphoric acid on the wettability and roughness of smear layer‐covered and smear layer‐free dentin. Materials and Method: Three self‐etching primers (Clearfil SE Bond, AdheSE, and Xeno III) and 10% (w/w) phosphoric acid (H3PO4) solution were evaluated. The substrates were midcoronal dentin with and without smear layer. For each liquid, pH, density, and surface tension were determined. Water wettability of dentin and roughness were measured before and after each etching. Wettability of self‐etching primers and phosphoric acid was measured on untreated dentin. Results: Water wettability increased after acid conditioning similarly for all the liquids used. On smear layer‐covered surfaces, self‐etching primers achieved a comparable wetting but with greater contact angles than phosphoric acid. However, on smear layer‐free surfaces, the increasing sequence of contact angle was Clearfil SE < AdheSE < Xeno III < Phosphoric acid. The treatment with phosphoric acid (lowest pH) produced the highest roughness increase on both dentin substrates. The roughening effect of the self‐etching adhesives was more evident for AdheSE and Xeno III. Conclusions: Self‐etching primers and phosphoric acid promote similar water wettability increase. However, self‐etching primers provided lower dentin roughness increase than pretreatment with phosphoric acid. The presence of smear layer did not affect the results of self‐etching and phosphoric acid treatments. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008